I wouldn't think twice about whether the envelope was hand written or printed.... I don't think any "normal" person would comment on it.
Now, on the other hand, I once received a wedding invitation that was SO cheesy, it was bordering on rude. This former roommate has a brother who is a professional baseball player, and she had a NICE wedding with his help... Her invitation, I kid you not, was a fold-open cardstock thing with a DETACHABLE reply postcard!! Like a piece of junk mail that you get to subscribe to a magazine! Complete with the little circular sticker that sealed the thing closed! Tear the sticker in half, fold open twice, read the invite, and if you wanna come, fold and tear at the perforation and mail back your reply card! Where does a person even FIND such a thing! I am not a snob... If she were flat broke and doing the best she could, I wouldn't have thought twice about it... but when you have your millionaire brother forking over big cash for your wedding, and you're registered for cappuccino machines at Pottery Barn, THIS was the best you could come up with for invitations?!?